This invention relates to a private branch exchange (hereinafter referred to as PBX) capable of performing the mode setting by which the type (hereinafter referred to as dial mode) of a dial or selection signal transmitted from the PBX to a central office line connected thereto is set to be of either a dual tone modulated-frequency signal (hereinafter referred to as DTMF signal) or a pulsed dial signal (hereinafter referred to as pulsed signal).
A PBX related to the present invention is shown in FIG. 5 and it operates as will be described with reference to FIGS. 6 and 7. The PBX shown in FIG. 5 is generally designated by reference numeral 500 and is constructed of components to be described below.
A relay 502 for acquiring a central office line 508 is controlled by a controller 501 in order that establishment/release of a DC loop for a central office exchange 509 is carried out to inform the exchange 509 of transmission, response or clear-down by the PBX, and when the line 508 is acquired for signal transmission, the DC loop is turned on and off intermittently to transmit the pulsed signal. A capacitor 503 is adapted to block the DC signal on the line 508 and pass only a talking sound band signal to a channel unit 505. A DTMF signal transmitter 504 is connected to the capacitor 503 and operated under the control of the controller 501 to transmit a DTMF signal to the exchange 509 by way of the line 508. The channel unit 505 is operated also under the control of the controller 501 to establish connection of the talking sound band signal between the line 508 and an extension. A memory 506 coupled to the controller 501 has a program area PA for storing a program which accords with flow charts as shown in FIGS. 6 and 7, and the controller 501 executes a series of processings in accordance with the program. The memory 506 also has a memory area MA for storing a series of dial signal data transmitted from the extension and information about the dial mode for line 508 which has been registered in advance by means of a console 507. The console 507 is coupled to the controller 501 and used, when the PBX unit is installed or the PBX is required to be inspected for maintenance, to allow the operator to input a program and observe information display. The controller 501 is operable to control the previously-described components in accordance with the control program stored in the program area PA of the memory 506.
The flow charts of FIGS. 6 and 7 are useful to explain the operation of the PBX 500 shown in FIG. 5.
In particular, the dial mode for the central office exchange 509 can be determined by means of the console 507 in accordance with the FIG. 6 flow chart indicative of programming of the dial mode.
In step 601, the operator manipulates the console 507 to input the programming to the controller 501. In step 602, the dial mode for the exchange 509 is decided on the basis of the thus inputted programming data. If the DTMF signal mode is selected, information to that effect is set in the memory area MA of the memory 506 in step 603. If the pulsed signal mode is selected, information to that effect is set in the memory area MA in step 604.
Then, a dial or selection signal is transmitted to the line 508 in accordance with the flow chart shown in FIG. 7.
In step 701, the relay 502 is turned on to acquire the line 508. Subsequently, in step 702, the dial mode previously registered in the memory area MA of the memory 506 by means of the console 507 is decided. If the dial mode is determined to be the DTMF signal mode, it is decided in step 703 whether dial data transmitted from the extension is present in the memory area MA of the memory 506. If present, in step 704, the DTMF signal transmitter 504 is driven to transmit one digit of the dial data in the form of the DTMF signal and thereafter the procedure returns to the preceding step 703, at which the presence of dial data in the memory area MA is again decided. The processing through the steps 703 and 704 is repeated until the transmission of all dial data is completed. Conversely, if the absence of dial data in the memory area is decided in step 703, the procedure proceeds to step 707 for ordinary talking processing, thus completing the dial transmission processing.
If the dial mode is determined to be the pulsed signal mode in step 702, the procedure proceeds to step 705 at which it is decided, as in the case of the step 703, whether dial data is present in the memory area MA. If present, the procedure proceeds to step 706 at which the relay 502 is driven to transmit one digit of the dial data in the form of the pulsed signal to the line 508 and thereafter the procedure returns to the step 705. Then, the processing through the steps 705 and 706 is repeated until the transmission of all dial data stored in the memory area MA is completed. Thereafter, when the absence of dial data is determined in step 705, the procedure proceeds to step 707 for ordinary talking processing, thus completing the dial transmission processing.